1. Field of the Invention
The present invention relates to a multi-hole film cooled combustor liner for use in a gas turbine for a regular power generation system, and a method of manufacture
2. Information of the Related Art
A gas turbine for a regular power generation system, for example, a heavy-duty-type gas turbine, generally comprises a combustors located between a compressor and a turbine. In the combustor of this type, compressed air is supplied from the compressor into the combustor, and fuel ejected from a fuel injection valve is mixed and burned with the compressed air. A resultant combustion gas is cause to flow into the turbine, and usually has an intensely high temperature such as 2,000.degree. C. To prevent the intense heat of the hot gas from damaging the turbine, the temperature of the gas at the outlet of the combustor must be made lower to an acceptable level such as 1,300.degree. C. Thus, a great deal of air is required to cool the hot gas during the gas turbine operation.
Conventionally, as shown in FIG. 11 or 12, a film cooled combustor liner is provided in the combustor. A liner shell 1 is in the form of a wavy thin-walled cylinder, and inner rings 2 are attached to the inside of the shell 1. A large number of film cooling holes 3 are drilled through the wall of the liner shell 1. Air admitted through the cooling holes 3 is deflected by the inner rings 2 to flow along the inside of the liner in the flowing direction for the combustion gas. Thus, a cooling film is maintained along the inside of the liner, thereby efficiently cooling the gas passing through the liner to the turbine. As a result, the temperature of the combustion gas admitted into the turbine is lowered to the acceptable level. Further, fins 4 for improving the buckling strength of the combustor liner are attached by TIG welding or the like on the outer peripheral surface of the liner shell 1 on the downstream side.
As the liner shell 1 require strength at high-temperatures, an Ni- or Co-based alloy, a hardly workable material, is used as a base material for the liner shell 1. The liner shell 1 of this material is manufactured by a method shown in FIG. 13A or 13B.
According the manufacturing method shown in FIG. 13A, the cooling holes 3 are drilled through a flat member or plate by punching or drilling in Step S1, the flat member is curved into a cylindrical shape in Step S2, and the cylindrical member is welded in the longitudinal direction by TIG welding or the like in Step S3. In Step S4, moreover, the welded cylindrical member is formed into a wavy shape by spinning. As is also shown in FIG. 14, the welded cylindrical member 6 is rotated as a roller 5 is externally pressed against a die 7 set inside the welded cylindrical member 6. Thus, the welded cylindrical member 6 is formed into a wavy shape. Then, in Steps S5 or S6, the inner rings 2 are bonded to the liner shell 1 by resistance spot welding or vacuum brazing. In Step S7, fins 4 are bonded to the liner shell 1 by TIG welding or the like.
On the other hand, according the manufacturing method shown in FIG. 13B, a flat member or plate is curved into a cylindrical shape in Step S1, the cylindrical member is welded in the longitudinal direction by TIG welding or the like in Step S2, and the welded cylindrical member is formed into a wavy shape by spinning in Step S3 in the manner shown in FIG. 14. In Step S4, moreover, the cooling holes 3 are drilled through the wavy cylindrical member by punching or drilling. In Steps S5 or S6, the inner rings 2 are bonded to the liner shell 1 by resistance spot welding or vacuum brazing. In Step S7, fins 4 with a length of about 1 mm are bonded to the liner shell 1 by TIG welding or the like.
According the manufacturing method shown in FIG. 13A, however, the liner shell 1 is formed into the wavy shape after the cooling holes 3 are drilled therethrough, whereupon the configuration of the cooling holes 3 may possibly be deteriorated. In some cases, moreover, the cooling holes 3 fail to be arranged in appropriate position in the wavy wall of the liner shell 1.
According the manufacturing method shown in FIG. 13B, the punching process requires replacement of a used punch or other tool, and repairing the liner shell 1 takes much time when the punch is broken, even though the liner shell 1 is accurately formed into the wavy shape. In boring the cooling holes 3 by drilling, moreover, a predrilling process which is a requisite for the drilling operation takes more time than the punching process.
In the case where the inner rings 2 are attached to the liner shell 1, in either of the manufacturing methods shown in FIGS. 13A and 13B, they must be expanded, spot-welded, and brazed, wherefore it is very difficult to maintain the quality of brazed portions and attach the rings 2 in a short period of time.
Furthermore, since the reinforcement fins 4 bonded to the liner shell 1 by TIG welding are liable to substantial thermal deformation, furthermore, the liner results in having an unsatisfactory buckling strength.